Controller for data recorder

ABSTRACT

A controller for controlling interruptions and restarts when writing data to a recording medium by emitting a laser beam against the recording medium. The controller prevents buffer underrun errors. The laser beam is emitted at a high power level when writing data on the recording medium and at a low power read level when reading data from the medium. The writing of data is interrupted when there is a possibility of a buffer underrun error. When restarting data writing from where the interruption occurred, the laser beam is shifted from the read level to the write level before reaching the location at which the interruption occurred. This guarantees that the laser beam has the required power level when writing is restarted.

RELATED APPLICATIONS

This application is a continuation and claims the benefit of priorityunder 35 USC 120 of U.S. application Ser. No. 09/718,155, filed Nov. 21,2000. The disclosure of the prior application is considered part of andis incorporated by reference in the disclosure of this application. Thisapplication also claims the benefit of priority under 35 USC 119 ofJapanese application serial numbers 11-331418, filed Nov. 22, 1999 and2000-322074, Filed Oct. 23, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a data recorder, and more particularly,to a controller for a data recorder having a buffer memory for storingdata provided from an external device and recording the stored data ofthe buffer memory on a recording medium.

An optical disc recorder records data on an optical disc, which servesas a recording medium. A CD-DA family compact disc-recordable (CD-R)drive is one type of optical disc recorder that is widely used. A CD-Ris a so-called write-once optical disc on which data is written onlyonce. The recorded data cannot be physically deleted. A laser beam isirradiated against the optical disc from an optical head of the CD-Rdrive. The heat of the laser beam melts a dye and forms recording pitson a recording layer of the optical disc. Data is recorded on the discby changing the reflecting rate of the recording layer.

The optical disc recorder includes a buffer memory and an encoder. Thebuffer memory temporarily stores data provided from an external device,such as a personal computer. The encoder reads the data from the buffermemory and encodes the read data to record the data on the optical disc.

In such an optical disc recorder, if, for example, the rate of datatransmission from the external device is slower than the recording datatransmission rate of the optical disc (write speed), the transmissionrate of the recording data output from the encoder is faster than thetransmission rate of the data provided to the buffer. This decreases theamount of data stored in the buffer memory. If the decrease continues,the data amount ultimately becomes null and the buffer memory becomesempty. This stops the stream of data to the encoder and causes aninterruption in the data recorded on the optical disc. This problem isreferred to as buffer underrun. The interruption in the data recorded onthe optical disc resulting from buffer underrun is referred to as abuffer underrun error.

Data is recorded on an optical disc using a recording technique thatdesignates the file group recorded on the optical disc (e.g., disc atonce, track at once). Thus, if a buffer underrun error occurs, theentire optical disc becomes unusable when employing disc at once, andthe track undergoing recording becomes unusable when employing track atonce.

Recent CD-R drives record data at a speed four times or eight times thenormal recording speed. Further, recent personal computers havemultitasking functions to operate CD-R drives. This has increased thetendency of the occurrence of buffer underrun errors.

Packet writing is one type of data recording that records data in packetunits. Packet writing records data on an optical disc when the datareaches the capacity of the packet. This prevents the occurrence ofbuffer underrun errors. However, link blocks must be formed to connectpackets in packet writing. The link blocks decrease the recordingcapacity of the optical disc. Further, there are CD-ROM drives that arenot capable of handling packet writing. Such CD-ROM drives cannotreproduce data written to optical discs through packet writing. In otherwords, the CD-ROM compatibility required by the CD-R standard (OrangeBook Part II) does not include packet writing. For example, packetwriting cannot be applied for a CD-DA player. Thus, a CD-R drive cannotrecord CD-DA audio data through packet writing. Accordingly, there is aneed for preventing buffer underrun errors without employing packetwriting.

A CD-rewritable (CD-RW) drive is another type of optical disc recorderthat is widely used. A CD-RW drive irradiates a laser beam from anoptical head against an optical disc. The heat of the laser beam causesphase changes between amorphic and crystalline to form recording pits onthe recording layer of the optical disc. This changes the reflectingrate of the recording layer and records data on the optical disc. Datacan be repeatedly rewritten to optical discs used by the CD-RW drive.Accordingly, the optical disc remains usable even if a buffer underrunerror occurs. However, when a buffer underrun error occurs, the datafile that was being recorded before the occurrence of the bufferunderrun error must be recorded again. This wastes the recordingperformed prior to the occurrence of the buffer underrun error andincreases the recording time.

A magneto-optic disc recorder is another type of known data recorder.The magneto-optic disc recorder irradiates a laser beam from an opticalhead against a magneto-optic disc. This applies residual magnetizationto the recording layer of the optical disc and records data on themagneto-optic disc. Mini disc (MD) drives are widely used magneto-opticdisc recorders. However, MD drives have the same problem as CD-RWdrives.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a controller for adata recorder that controls data recording in a manner that thecontinuity of the data is ensured even if the recording of data to arecording medium is interrupted.

To achieve the above object, the present invention provides a controllerfor controlling interruption and restarting data writing to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium at a write level that is in accordance with dataread from a buffer memory. The controller includes an address memory forstoring at least one of an address of the recording medium and anaddress of the buffer memory when the writing of data to the recordingmedium is interrupted. Each address indicates a data location where thewriting interruption occurred. A synchronizing circuit reads the datawritten to the recording medium prior to the interruption by emittingthe laser beam at a read level, reading the data stored in the buffermemory, and synchronizing the written data and the stored data. Arestart circuit restarts the data writing based on the address stored inthe address memory. The restart circuit switches the laser beam from theread level to the write level before the restart circuit restarts thedata writing.

A further aspect of the present invention provides a controller forcontrolling interruption and restarting data writing to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium in accordance with data read from a buffer memory.The controller includes an address memory for storing at least one of anaddress of the recording medium and an address of the buffer memory whenthe writing of data to the recording medium is interrupted. Each addressindicates a location of data when the writing interruption occurred. Asynchronizing circuit reads the data written to the recording mediumprior to the interruption by emitting the laser beam, reads the datastored in the buffer memory, and synchronizes the written data and thestored data. A restart circuit generates an instruction for restartingthe writing of data to the recording medium based on the address storedin the address memory. The restart circuit generates the instruction forrestarting the writing of data before the data read from the recordingmedium by the synchronizing circuit reaches the interruption location.

Another aspect of the present invention provides a controller forcontrolling interruption and restarting data writing to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium with a power that is in accordance with data readfrom a buffer memory and supplied from a power source. The controllerincludes an address memory for storing at least one of an address of therecording medium and an address of the buffer memory when the writing ofdata to the recording medium is interrupted. Each address indicates adata location where the writing interruption occurred. A synchronizingcircuit reads the data written to the recording medium prior to theinterruption by emitting the laser beam, reads the data stored in thebuffer memory, and synchronizes the written data and the stored data. Arestart circuit restarts data writing based on the address stored in theaddress memory. The power source is activated prior to the time when thewriting of data is restarted.

A further aspect of the present invention provides a method forcontrolling interruption and restarting of writing data to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium at a write level that is in accordance with dataread from a buffer memory. The method includes storing at least one ofan address of the recording medium and an address of the buffer memorywhen the writing of data to the recording medium is interrupted. Eachaddress indicates a data location where the writing interruptionoccurred. The method further includes reading the data written to therecording medium prior to the writing interruption by emitting the readlevel laser beam against the recording medium and reading the datastored in the buffer memory, synchronizing the written data and thestored data, generating an instruction for restarting data writing tothe recording medium based on the address stored in the address memory,and shifting the laser beam from the read level to the write levelbefore writing is restarted.

Another aspect of the present invention provides a method forcontrolling interruption and restarting of data writing to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium in accordance with data read from a buffer memory.The method includes storing at least one of an address of the recordingmedium and an address of the buffer memory when the writing of data tothe recording medium is interrupted. Each address indicates a datalocation where the writing interruption occurred. The method furtherincludes reading the data written to the recording medium prior to thewriting interruption by emitting the laser beam against the recordingmedium and reading the data stored in the buffer memory, synchronizingthe written data and the stored data, and generating an instruction forrestarting data writing based on the address stored in the addressmemory. The writing is restarted before the location of the data readfrom the recording medium in the reading step reaches the interruptionlocation.

A further aspect of the present invention provides a method forcontrolling interruption and restarting data writing to a recordingmedium. The data writing is performed by emitting a laser beam againstthe recording medium at a power level that is in accordance with dataread from a buffer memory and supplied from a power source. The methodincludes storing at least one of an address of the recording medium andan address of the buffer memory when the writing of data to therecording medium is interrupted. Each address indicates a data locationwhere the writing interruption occurred. The method further includesreading the data written to the recording medium prior to the writinginterruption by emitting the laser beam and reading the data stored inthe buffer memory, synchronizing the written data and the stored data,generating an instruction for restarting the writing of data to therecording medium based on the address stored in the address memory, andactivating a power source for generating power of the laser beam priorto the restart of the writing of data.

Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a schematic block diagram showing a CD-R drive according to apreferred embodiment of the present invention;

FIG. 2( a) is a schematic cross-sectional view showing a recordingmedium during the interruption of data recording;

FIG. 2( b) is a schematic cross-sectional view showing the recordingmedium when a laser is activated from an interrupt position to restartthe data recording;

FIG. 2( c) is a schematic cross-sectional view showing the recordingmedium when the laser is activated before the laser reaches theinterrupt position to restart the data recording;

FIG. 3 is a schematic block diagram showing a laser drive circuit of theCD-R drive of FIG. 1;

FIG. 4( a) is a schematic diagram showing a sector of an optical disc;and

FIG. 4( b) is a diagram illustrating addresses of a buffer memory of theCD-R drive of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1, a CD-R drive 1 includes a spindle motor 2, aspindle servo circuit 3, an optical head 4, an RF amplifier 5, a headservo circuit 6, a decoder 7, a subcode decoding circuit 8, a wobbledecoder 9, an ATIP decoding circuit 10, an external connection terminal11, an interface 12, a buffer memory 13, an encoder 14, an encoderinternal RAM 15, a laser drive circuit 16, a laser drive circuitinternal memory (level memory) 17, a crystal oscillation circuit 18, anaccess control circuit 19, a buffer underrun determination circuit 20, arecording control circuit 21, and a system control circuit 22. The CD-Rdrive 1 is connected to a personal computer 31 via the externalconnection terminal 11 to record data, which is provided from thepersonal computer 31, on an optical disc 32 that complies with the CD-Rstandards. Further, the CD-R drive 1 provides the personal computer 31with data reproduced from the optical disc 32.

The spindle motor 2 rotates the optical disc 32. The spindle servocontrol circuit 3 controls the spindle motor 2 so that the optical disc32 is rotated using the constant linear velocity (CLV) method inaccordance with the rotation control signal generated by the wobbledecoder 9.

When reading data, the optical head 4 irradiates a relatively weak laserbeam against the optical disc and, from the reflected laser beam,generates a RF signal (high frequency signal) in correspondence with thedata recorded on the optical disc. When recording data, the optical head4 irradiates a relatively intense laser beam (several tens of timesgreater than the data reading laser beam) against the optical beam 32 toform recording pits on the recording layer of the optical disc 32 andchange the reflecting rate of the recording layer to record data. Insynchronism with the recording of data, the optical head 4 generates theRF signal in correspondence with the recorded data from the reflectedlaser beam.

The RF amplifier 5 amplifies the RF signal, which is provided from theoptical head 4, and digitizes the amplified RF signal to generate adigital data signal. The RF signal of the optical head 4 is fed back tothe head servo circuit 6 via the RF amplifier 5. The head servo circuit6 uses the RF signal to perform focusing control, tracking control, andsled feed control. Focusing control focuses the laser beam on therecording layer of the optical disc 32. Tracking control tracks thelaser beam along a signal track of the optical disc 32. Sled feedcontrol moves the optical head 4 in the radial direction of the opticaldisc 32.

The decoder 7 decodes the digital data provided from the RF amplifier 5.Further, the decoder 7 generates a pit clock from the digital data andseparates a subcode from the digital data to generate a subcodesynchronizing signal.

The subcode decoding circuit 8, which is incorporated in the decoder 7,decodes the subcode. Further, the subcode decoding circuit 8 generatessubcode Q channel data (hereafter referred to as sub-Q data) from thedecoded subcode.

The wobble decoder 9 extracts a wobble component of 22.05 kHz from apre-groove signal of the optical disc 32 that is included in the digitaldata provided from the RF amplifier 5. Then the wobble decoder generatesthe rotation control signal of the optical disc 32 from the wobblecomponent.

The ATIP decoding circuit 10, which is incorporated in the wobbledecoder 9, uses the wobble component to decode an absolute time inpre-groove (ATIP) and extract absolute time information, or an ATIPaddress, from the ATIP. The absolute time information indicatesaddresses of locations in the recording medium.

The interface 12 controls data transmission between the personalcomputer 31 and the CD-R drive 1.

The buffer memory 13 is a ring buffer that includes a synchronousdynamic random access memory (SDRAM), which preferably has a FIFOconfiguration, and the buffer memory 13 stores data provided from thepersonal computer 31 via the interface 12. Data stored at one address ofthe buffer memory 13 corresponds to data recorded at one sector of theoptical disc 32.

An interrupt/restart circuit 43 of the system control circuit 22controls the encoder 14. The encoder 14 reads the data stored in thebuffer memory 13 in sector units and encodes the data into recordingdata for the optical disc 32. The RAM 15, which is incorporated in theencoder 14, stores the necessary data for encoding by the encoder 14 andintermediate operation encoding data. When performing data encoding incompliance with the CD-ROM standard, the encoder 14 adds a synch byte, aheader, CD-ROM data error detection code (EDC), and an error correctioncode (ECC) to the data. The encoder 14 further performs error correctionusing a cross interleaved Reed-Solomon code (CIRC), which is a CD errorcorrection code, and eight to fourteen modulation (EFM) on the data.Further, the encoder 14 adds a subcode, which includes the sub-Q data,and a synchronizing signal of the subcode to the data.

The interrupt/restart circuit 43 also controls the laser drive circuit16, which provides a laser drive signal to the laser beam source of theoptical head 4. The laser drive circuit internal memory 17 stores datarelated to the voltage of the laser drive signal output from the laserdrive circuit 16. The voltage of the drive signal is constant whenreproducing data and varied in accordance with the recording data outputfrom the encoder 14 when recording data. When the recording data outputfrom the encoder 14 is low (L), recording pits are not formed on therecording layer of the optical disc 32. Thus, the drive signal is set sothat its voltage is the same as when data is reproduced. When therecording data is high (H), recording pits are formed on the recordinglayer of the optical disc 32. Thus, although the voltage of the drivesignal differs between track positions, the drive signal is set so thatits voltage is several tens of times greater than during datareproduction.

The crystal oscillation circuit 18 generates an oscillation signal basedon the oscillation of a crystal oscillator.

The access control circuit 19 selectively refers to the subcode addressof the absolute time information in the sub-Q data and the ATIP addressof the absolute time information in the ATIP to control the recordingcontrol circuit 21 and the head servo circuit 6. This controls access tothe optical disc 32.

The data provided to the buffer memory 13 is stored in the buffer memory13 in a predetermined address order. The buffer underrun determinationcircuit 20 directly or indirectly determines the amount of data storedin the buffer memory 13 from the address at which writing or reading ispresently performed. Based on the data amount, the buffer underrundetermination circuit 20 determines whether or not the buffer memory 13is in a state in which buffer underrun may occur.

Based on the determination result of the buffer underrun determinationcircuit 20 and in response to a command provided from the personalcomputer 31, the recording control circuit 21 controls the interface 12,the access control circuit 19, and the system control circuit 22.

The system control circuit 22 includes a system clock generation circuit41, a signal synchronizing circuit 42, the interrupt/restart circuit 43,a retry determination circuit 44, location detection circuits 45, 46,and address memories 47, 48. These circuits 41–48 are laid out on thesame chip of an LSI substrate.

The system clock generation circuit 41 generates from the oscillationsignal of the crystal oscillation circuit 18 a reference clock used whenrecording data. Further, the generation circuit 41 uses a pit clockextracted by the decoder 7 to generate a reproduction clock used whenreproducing data. The generation circuit 41 selects the reference clockor the reproduction clock in accordance with the switching controlperformed by the signal synchronizing circuit 42. The selected clock isused as a system operational clock of the CD-R drive 1. In accordancewith the operational clock, the CD-R drive 1 controls thesynchronization of the circuits 7–10, 12–16, and 19–22.

In accordance with the synchronizing signal of the subcode from thedecoder 7 and the sub-Q data from the subcode decoding circuit 8, thesignal synchronizing circuit 42 controls the recording control circuit21 so that the recording data output from the encoder 14 is synchronizedwith the data recorded on the optical disc 32. When performing thiscontrol, the sub-Q data of the subcode decoding circuit 8 is associatedwith the sub-Q data of the encoder 14 after synchronizing the subcodesynchronizing signal of the decoder 7 with the subcode synchronizingsignal of the encoder 14. The signal synchronizing circuit 42 controlsthe system clock generation circuit 41 so that the reference clock orthe reproduction clock is output.

The recording control circuit 21 controls the interrupt/restart circuit43. The interrupt/restart control circuit 43 controls the encoder 14 andthe laser drive circuit 16 and, when the buffer underrun determinationcircuit determines that the buffer memory 13 has entered a state inwhich buffer underrun may occur, provides the address memories 47, 48with a recording interrupt signal.

The address memory 47 stores the address of the read data in the buffermemory 13 when receiving the recording interrupt signal from theinterrupt/restart circuit 43.

The address memory 48 stores the address of the ATIP decoded by the ATIPdecoding circuit 10 when receiving the recording interrupt signal fromthe interrupt/restart circuit 43.

When data is reproduced during a recording restart mode (describedlater), the location detection circuit 45 compares the address of thedata read from the buffer memory 13 with the address stored in theaddress memory 47. If the data address and the stored address are thesame, the location detection circuit 45 activates the recording restartsignal.

When data is reproduced during the recording restart mode, the locationdetection circuit 46 compares the address of the ATIP decoded by theATIP decoding circuit 10 with the ATIP address stored in the addressmemory 48. If the decoded ATIP address and the stored ATIP address arethe same, the location detection circuit 46 activates the recordingrestart signal.

The retry determination circuit 44 instructs the recording controlcircuit 21 to restart the recording operation of the interface 12, theaccess control circuit 19, and the system control circuit 22 when therestart signals of the location detection circuits 45, 46 aresimultaneously activated. When the two restart signals are notsynchronously activated (when the restart signals are activated atdifferent timings), the retry determination circuit 44 instructs thecontrol circuit 21 to repeatedly perform data reproduction in therecording restart mode until the two restart signals are synchronouslyactivated.

The operation of the CD-R drive 1 will now be discussed.

When a user manipulates the personal computer 31 to record data, thepersonal computer 31 generates a command accordingly. The command istransferred to the recording control circuit 21 via the interface 12. Inresponse to the command, the recording control circuit 21 controls theinterface 12, the access control circuit 19, and the system controlcircuit 22 to record data.

When recording begins, the signal synchronizing circuit 42 switches theoperational clock output of the system clock generation circuit 41 tothe reference clock. As a result, the circuits 7–10, 12–16, 19–22 of theCD-R drive 1 are synchronized with the operational clock, or thereference clock.

The data provided from the personal computer 31 is stored in the buffermemory via the interface 12 and read from the buffer memory 13 in sectorunits. The encoder 14 encodes the data read from the buffer memory 13 insector units to generate recording data. The laser drive circuit 16provides the optical head 4 with drive signal having a voltagecorresponding to the recording data. In accordance with the drivesignal, the optical head 4 changes the intensity of the laser beamirradiated against the optical disc 32. This forms recording pits on therecording layer of the optical disc 32 and records data on the opticaldisc 32. Simultaneously, from the laser beam reflected by the opticaldisc 32, the optical head 4 reproduces the data recorded on the opticaldisc 32 as the RF signal. The RF amplifier 5 amplifies the RF signalprovided from the optical head 4 to generate digital data. The wobbledecoder 9 extracts the wobble component from the digital data and usesthe wobble component to generate the rotation control signal. Inaccordance with the rotation control signal, the spindle servo circuit 3controls the spindle motor 2 so that the optical disc 32 is rotated at aconstant linear velocity. The ATIP decoding circuit 10 decodes the ATIPusing the wobble component and extracts the ATIP address of the absolutetime information in the ATIP.

When the transmission rate of the data provided from the personalcomputer 31 is slower than the transmission rate of the data recorded inthe optical disc 32 (write speed), that is, when the transmission rateof the data provided to the buffer 13 is slower than that of the dataoutput from the encoder 14, the amount of data stored in the buffermemory 13 decreases. When the buffer underrun determination circuit 20determines that a buffer underrun error may occur in the buffer memory13, the recording control circuit 21 controls the interrupt/restartcircuit 43 so that, before the occurrence of a buffer underrun in thebuffer memory 13, the address memories 47, 48 are accordingly providedwith the interrupt signal and the output of recording data from theencoder 14 is interrupted. In response to the interrupt signal, theaddress memories 47, 48 store the data address of the buffer memory 13.In other words, the address memory 47 stores the buffer memory addressof the data read from the buffer memory 13 when receiving the interruptsignal. The address memory 48 stores the ATIP address of the ATIPdecoding circuit 10 when receiving the interrupt signal.

When the output of the recording data from the encoder 14 isinterrupted, the transmission of the drive signal from the laser drivecircuit 16 to the optical head 4 is impeded. This stops the emission ofthe laser beam from the optical head 4 and interrupts the recording ofdata on the optical disc 32.

When the interrupt/restart circuit 43 outputs the interrupt signal, thesector of the data being output from the encoder 14 is recorded on theoptical disc 32. It is preferred that the interrupt signal of theinterrupt/restart circuit 43 be output at times between sectors of therecording data. The interrupt/restart circuit 43 stores in the memory 17the voltage data of the laser drive signal output from the laser drivecircuit 16 when the recording is interrupted.

Subsequent to the recording interruption, the data provided from thepersonal computer 31 is stored in the buffer memory 13 via the interface12. As the amount of data stored in the buffer memory 13 increases, thestate in which a buffer underrun may occur no longer exists. When thebuffer underrun determination circuit 20 determines that buffer underrunis not likely to occur, the recording control circuit 21 controls theaccess control circuit 19 and the system control circuit 22 to performdata reproduction in the recording restart mode.

When data reproduction is performed in the recording restart mode, theaccess control circuit 19 controls the head servo circuit 6. The headservo circuit 6 controls focusing, tracking, and sled feed of theoptical head 4 to move the optical head 4 to a sector location that isprior by a predetermined number of sectors from the sector at which therecording interruption occurred. The optical head 4 then irradiates thelaser beam from that sector location.

The interrupt/restart circuit 43 controls the laser drive circuit 16 sothat a drive signal having a constant voltage is output from the laserdrive circuit 16. This results in the optical head 4 irradiating theoptical disc 32 with a relatively weak laser beam. The reflected laserbeam reproduces the data recorded on the optical disc prior to therecording interruption, and the optical head 4 outputs the RF signal.The RF signal is amplified by the RF amplifier 5 and converted todigital data. The decoder 7 decodes the digital data, extracts a pitclock from the digital data, and separates a subcode from the digitaldata. A subcode synchronizing signal is generated from the subcode. Thesubcode is decoded by the subcode decoding circuit 8 to generate thesub-Q data.

When data reproduction in the recording restart mode is started, thesignal synchronizing circuit 42 switches the operational clock from thereference clock of the crystal oscillation circuit 18 to thereproduction clock of the decoder 7. The circuits 7–10, 12–16, 19–22 ofthe CD-R drive 1 are operated in accordance with the reproduction clock.By using the reproduction clock, the data recorded on the optical disc32 prior to the recording interruption is accurately reproduced.

The recording control circuit 21 controls the interrupt/restart circuit43 to instruct the encoder 14 to restart the output of the recordingdata. The encoder 14 goes back by a predetermined number of sectors fromthe data address of the buffer memory 13 at which the recordinginterruption occurred and starts reading data in sector units from thatsector of the buffer memory 13. The encoder 14 adds a synch byte, aheader, an EDC, and an ECC to the read data, performs the CIRC and EFMprocesses, and adds a subcode, which includes the sub-Q data, and thesubcode synchronizing signal to the read data.

The drive signal of the laser drive circuit 16 is constant during datareproduction in the recording restart mode. In other words, the drivesignal of the laser drive circuit 16 has a low voltage. Accordingly,laser irradiation does not affect the data recorded on the optical discprior to the interruption.

The signal synchronizing circuit 42 controls the access control circuit19 via the recording control circuit 21 and synchronizes the datarecorded on the optical disc 32 with the recording data output from theencoder 14. In other words, the signal synchronizing circuit 42 controlsthe recording control circuit 21 and the access control circuit 19 sothat the subcode synchronizing signal of the decoder 7 is synchronizedwith the subcode synchronizing signal of the encoder 14 and the sub-Qdata of the subcode decoding circuit 8 is associated with the sub-Q dataof the encoder 14.

The location detection circuit 45 compares the address of the data readfrom the buffer memory 13 with the address stored in the address memory47 and activates the restart signal when the data address and the storedaddress are the same. The address stored in the address memory 47 is theaddress of the data read from the buffer memory 13 when the recording ofdata is interrupted.

The location detection circuit 46 compares the ATIP address of the ATIPdecoding circuit 10 with the ATIP address stored in the address memory48 and activates the restart signal when the ATIP address and the storedaddress are the same. The ATIP address stored in the address memory 48is the ATIP address decoded by the ATIP decoding circuit 10 when therecording of data is interrupted.

When the restart signals of the location detection circuits 45, 46 aresimultaneously activated, the retry determination circuit controls theinterface 12, the access control circuit 19, and the system controlcircuit 22 via the recording control circuit 21. The signalsynchronizing circuit 42 switches the operational clock of the systemclock generation circuit 41 from the reproduction clock to the referenceclock when recording is restarted.

Upon the restart of the recording, the address of the data read from thebuffer memory 13 shifts to the address next to the address at which datarecording was interrupted. Further, the address memory 48 and thelocation detection circuit 46 shift the sector location of the opticaldisc 32 irradiated by the laser beam to the sector location next to thesector location at which data recording was interrupted. In this state,the signal synchronizing circuit 42 synchronizes the recording dataoutput from the encoder 14 with the data recorded on the optical disc32. Accordingly, the data of the sector next to the sector at which datarecording was interrupted is recorded upon the restart of the recording.In other words, sectors of data are recorded without any interruptionswhen restarting recording. This ensures the continuity of the recordeddata while preventing the occurrence of a buffer underrun error.

The interrupt/restart circuit 43 activates the power of the laser beamemitted from the optical head 4 a predetermined time t before the timeat which the restart of the recording operation becomes possible. Morespecifically, prior to the restart of the recording operation by thepredetermined time t, the interrupt/restart circuit 43 controls thelaser drive circuit 16 so that the laser drive circuit 16 provides theoptical head 4 with a drive signal having a voltage corresponding to thedata that was stored in the memory 17 when the recording operation wasinterrupted. This prevents the formation of a non-recording section onthe optical disc 32. Thus, the recorded data has no interruptions.

In other words, if the recording data output by the encoder 14 has ahigh level when the recording operation is interrupted, although thevoltage differs between track positions, the laser drive circuit 16outputs a drive signal having a voltage that is several tens of timesgreater than that when data is reproduced. The laser power of theoptical head 4 when the optical recording operation is interrupted isthus several tens of times greater than that when the reproductionoperation is being performed. However, the power of the laser beam ofthe optical head 4 cannot be activated instantaneously to a level thatis several tens of times greater then that of the reproductionoperation. Accordingly, a certain amount of time is necessary toactivate the power of the laser beam. That is, when activation the powerof the laser beam of the optical head when restarting the recordingoperation, a certain length of time is required for the laser power toreach the desired level. Such delay forms a non-recording section on theoptical disc 32 and interrupts the recorded data.

With reference to FIG. 2( a), a laser beam 101 is emitted against thesurface of a recording medium 100. This results in reaction of a dye atthe irradiated area and records data. In the example of FIG. 2( a), thelaser beam 101 is intermittently emitted against a section 102 of therecording medium 100 in accordance with the values “1” and “0” of therecording data to form a data section having a predetermined pattern.When the recording is interrupted at an interrupt position 103 on therecording medium 100, a data section 104 is not formed in the desiredmanner. In this case, recording is restarted from the interrupt position103 by performing data reproduction in the recording restart mode from apredetermined address. Referring to FIG. 2( b), it takes about severalmicroseconds to several tens of microseconds to increase the drivevoltage of the laser drive circuit 16 at the interrupt position 103 to alevel equal to that when the interruption occurred. Hence, during thisdelay period, the intensity of the emitted laser beam 101 is low and asection 105 at which the dye does not react is formed on the recordingmedium 100. Although the insufficient emission section 105 illustratedin FIG. 2( b) is short, several microseconds correspond to more than onehundred pulses of a clock. A synchronizing pattern allocated to thebeginning of a frame is data of successive zeros or ones. In thesynchronizing pattern, zeros or ones continue for 11 clock pulses. Theinsufficient emission-section 105 is about ten times longer than thesynchronizing pattern. Accordingly, the insufficient emission section105 may cause the reading of data to be unsatisfactory.

In the present invention, at a time that is earlier than the restart ofthe recording operation by the predetermined time t, the drive signalvoltage is set to the level that existed when the recording interruptionoccurred. This increases the laser power of the optical head 4. Thepredetermined time t corresponds to the time period required foractivating the power of the laser beam. In other words, referring toFIG. 2( c), the laser power is activated at a section 106 that includesa location corresponding to the predetermined time t prior to theinterruption position 103 of the recording medium 100. Thus, the laserpower reaches a sufficient level at the interrupt position 103, and thedesired data is recorded in a continuous manner on the section 104.

This procedure permits the recording operation to be restarted when thelaser beam has the same power as when the recording operation wasinterrupted. This prevents the formation of a non-recording section onthe optical disc 32. Thus, the recorded data has no interruptions.

Instead of setting the laser power of the optical head at the level thatexisted when the interruption occurred, the laser power may be set at alevel that is sufficiently high. In other words, if the drive signalvoltage is set at a sufficiently high level, the laser power may bedecreased to the required level within a short period of time whenrestarting the recording operation. This eliminates the need for thememory 17. However, if the laser power is set too high, the recordingpits formed on the recording layer of the optical disc 32 may be burnedout. Accordingly, it is preferred that the laser power of the opticalhead 4 be set at a level that does not burn out the recording pits.

When the two restart signals of the location detection circuits 45, 46are not synchronously activated (when the two restart signals areactivated at different times), the retry determination circuit 44repeatedly perform data reproduction in the recording restart mode untilthe two restart signals are synchronously activated. In other words, ifan external disturbance occurs for one reason or another (e.g., theapplication of an external impact to the CD-R drive), the elements 2–22of the CD-R drive 1 may function erroneously such that the two restartsignals are not synchronously activated. Thus, the retry determinationcircuit 44 repeats data reproduction to avoid the influence of anexternal disturbance. If the two restart signals of the locationdetection circuits 45, 46 are always simultaneously activated, the retrydetermination circuit 44, the location detection circuit 45, and theaddress memory 47 may be deleted.

As shown in FIG. 3, the laser drive circuit 16 includes two memories 17,202, two power sources 201, 203, two switches 204, 205, and an ANDcircuit 206.

The memory 17 stores write voltage data, which corresponds to the writelaser power. The power source 201 generates the write laser power inaccordance with the write voltage data stored in the memory 17. Thepower source 203 generates read laser power in accordance with readvoltage data stored in the memory 202. The AND circuit 206 receives theinterrupt/restart signal and a mode switching signal for switchingbetween a write mode and a read mode and outputs the switching signal ofthe switch 204. The level of the mode switching signal is high during awrite mode and low during a read mode. The interrupt/restart signal isnormally high.

During the write mode, the mode switching signal output by the ANDcircuit 206 is high. Thus, the switch 204 selects the power source 201.When an output signal of the encoder 14 is high, the switch 205 selectsthe output of the switch 204, provides the optical head 4 with the writelaser power of the power source 201, and emits the laser beam againstthe recording medium. When the output signal of the encoder 14 is low,the switch 205 is switched to a predetermined voltage L.

When recording is interrupted and the interrupt/restart signal isshifted to a low level, the switch 204 is connected to the power source203 and the output of the encoder 14 is stopped. Accordingly, the drivesignal provided to the optical head 4 has a low voltage incorrespondence with the read voltage data. This temporarily sets theread mode.

In a first method for activating the laser power provided from the powersupply 201 before recording is restarted, the power source 201 isactivated at a predetermined time t before recording is restarted. Forexample, during data reproduction in the recording restart mode, thepower source 201 is activated when the read address or the address ofthe buffer memory 13 matches an address that is a predetermined numberof addresses prior to that stored in the address memories 47 or 48.

In a second method for increasing the laser power before recording isrestarted, the restart/interrupt circuit 43 causes the interrupt/restartsignal to go high to restart writing when the read address or theaddress of the buffer memory 13 matches an address prior to that storedin the address memories 47 or 48 by a predetermined number of addressesx. In this case, the optical head 4 emits the laser beam against thesection on which data has already been recorded. However, since thelaser power is still low, the data on the recorded section is notrewritten. When the output of the power source 201 increases and thewrite laser power becomes sufficient, the emitted laser beam reaches theinterrupt position 103 of the recording medium 100. Accordingly, thepredetermined address number x is set to correspond with thepredetermined time t required for activating the laser power to therequired level.

The address of the interrupt position 103 may be stored in the addressmemories 47, 48 to advance the recording operation from the interruptposition 103. Alternatively, an address that is a predetermined numberof addresses prior to that of the interruption position 103 may bestored in the address memories 47, 48.

It is preferred that the predetermined time t be set experimentally inaccordance with the laser power increasing characteristic of the opticalhead 4. For example, the predetermined time t may be set severalmicroseconds to several tens of microseconds prior to the restart of therecording operation. The predetermined time t is determined based on thepulse count of the operational clock of the CD-R drive 1. When therecording speed of the CD-R drive 1 is set to 4× or 8×, the system clockgeneration circuit 41 generates an operational clock having a highfrequency. Accordingly, during high speed operations, the pulse count ofthe operational clock and the predetermined address number x must beincreased in accordance with the operational speed so that the laserpower activation of the optical head 4 is in time for the restart of therecording operation.

The memory 17 is preferably an eight bit (the bit number of the writevoltage data) latch circuit formed by flip-flops. The write voltage datalatched by the latch circuit is held when the recording is restarteduntil the laser power is activated to a sufficient level. In otherwords, the write voltage data held by the latch circuit is not correctedwhen the recording is restarted until the laser power increases to asufficient level.

FIG. 4( a) is a schematic view showing a sector of the optical disc 32.FIG. 4( b) is a diagram illustrating the addresses of the buffer memory13. Sectors Sn+1, Sn, Sn−1, Sn−2 . . . , Sn−m shown in FIG. 4( a) arerespectively associated with addresses An+1, An, An−1, An−2, . . . ,An−m shown in FIG. 4( b).

During recording, data is read from the buffer memory 13 in the order ofaddresses An−m, . . . , An−2, An−1, An, and the recording data encodedby the encoder 14 is recorded on the optical disc 32 in the order ofsectors Sn−m, . . . , Sn−2, Sn−1, Sn. For example, if the bufferunderrun determination circuit 20 determines during the recording ofdata that a bus underrun may occur at address An, the data of sector Sn,which is associated with address An, is recorded. However, the recordingof data is interrupted from the sector Sn+1, which is associated withaddress An+1.

When the recording of data is interrupted, address An is stored in theaddress memory 47, and the address of the ATIP decoded from the datarecorded at sector Sn is stored in the address memory 48. Afterward,when the buffer underrun determination circuit 20 determines that abuffer underrun is no longer likely to occur, data reproduction in therecording restart mode is commenced from sector Sn−m by going back fromsector Sn, at which recording was interrupted, by a predetermined numberof sectors (in this case, m sectors).

When data reproduction is commenced, data is read from the buffer memory13 from address An−m by going back from address An, at which recordingwas interrupted by a predetermined number of addresses (m addresses).The read data is encoded into recording data by the encoder 14.

The signal synchronizing circuit 42 synchronizes the recording dataoutput from the encoder 14 with the data recorded on the sectors Sn−m toSn of the optical disc 32. Then, when the address of the data read fromthe buffer memory 13 matches the address An stored in the address memory47, the restart signal of the location detection circuit 45 isactivated. When the address of the ATIP decoded by the ATIP decodingcircuit 10 matches the ATIP address of the sector Sn stored in theaddress memory 48, the restart signal of the location detection circuit46 is activated. When the two restart signals of the location detectioncircuits 45, 46 are simultaneously activated, the retry determinationcircuit 44 restarts the recording of data from sector Sn+1, which isnext to the sector Sn at which data recording was interrupted.

It is preferred that the predetermined sector number (m sectors) besufficient for obtaining time period T1, which is required for thespindle serve circuit 3 to control the spindle motor 2 and the headservo circuit 6 to control the optical head 4, and time period T2, whichis required for synchronization by the signal synchronizing circuit 42.For example, m is set at 10 to 30. The time periods T1, T2 increase asthe recording speed of the CD-R drive 1 becomes higher, for example, asthe recording speed increases from 4× to 8×. Accordingly, it ispreferred that the predetermined sector number be increased as therecording speed increases.

In the present invention, the power of the laser emitted against therecording medium is activated before restarting the recording operation.Thus, the laser beam emitted when the recording operation is restartedhas a sufficient power level. Accordingly, non-recorded sections are notformed on the recording medium. This prevents interruptions in therecorded data.

Further, the interrupt/restart circuit 43 instructs the restart of therecording before the read position of the recording medium reaches theinterruption position 103. Thus, the emitted laser beam has a sufficientpower level for writing from the interruption position. Accordingly,non-recorded sections are not formed on the recording medium. Thisprevents interruptions in the recorded data.

Additionally, the power level of the laser beam at the time point whenthe recording operation is interrupted is stored in the memory 17. Thelaser power level is activated beforehand based on the power levelstored in the memory 17. Accordingly, a laser beam having the optimalpower level is emitted. This prevents the formation of non-recordedsections on the recording medium.

It should be apparent to those skilled in the art that the presentinvention may be embodied in many other specific forms without departingfrom the spirit or scope of the invention. Particularly, it should beunderstood that the present invention may be embodied in the followingforms.

(1) The present invention may be applied to a data recorder employingthe constant angular velocity (CAV) method. In such case, a clocksynchronized with the wobble component, which is extracted by the wobbledecoder 9, is generated and used as the operational clock during therecording of data.

(2) The access control circuit 19, the buffer underrun determinationcircuit 20, the recording control circuit 21, and the system controlcircuit 22 may be replaced by a microcomputer that includes a CPU, aROM, and a RAM. In other words, the function of each circuit may beachieved by having a microcomputer perform various operations.

(3) The present invention may be applied to a data recorder (e.g., CD-RWdrive, MD drive) that uses a rewritable recording medium (e.g., CD-RWstandard optical disc, MD standard optical disc). In such case, theoccurrence of a buffer underrun error is prevented. This decreases thetime required for the recording of data.

(4) The present invention may be applied when data writing isinterrupted due to the displacement of the optical head 4. Data writingto the optical disc 32 is also interrupted when the relative positionbetween the optical head 4 and the optical disc 32 is offset due to aphysical impact or a mechanical deficiency. In such case, the presentinvention may be applied to restart the writing of data from theinterrupted position. For the restart of data writing, a mechanism fordetermining the displacement of the optical head 4 may be used in lieuof the buffer underrun determination circuit 20. The displacementdetermination mechanism may be formed by a vibration sensor, whichdetects external vibrations of the optical disc 32, a detection circuit,which detects a tracking error of the optical head 4 relative to theoptical disc 32, or the like.

The present examples and embodiments are to be considered asillustrative and not restrictive, and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. A controller for controlling interruption and restarting data writingto a recording medium, wherein writing the data stored in a buffermemory to the recording medium or reading the written data from therecording medium is performed by selectively providing an optical headperforming a laser irradiation with a write laser power source or a readlaser power source, the controller comprising: an address memory forstoring at least one of an address of the recording medium and anaddress of the buffer memory when the writing of data to the recordingmedium is interrupted, each address indicating a location where thewriting interruption occurred; and a restart circuit for generating aninstruction for restarting the writing of data to the recording mediumby changing the power source provided to the optical head from the readlaser power source to the write laser power source based on the addressstored in the address memory while reading the written data from therecording medium by providing the optical head with the read laser powersource, wherein the restart circuit generates an instruction for settingthe voltage of the write laser power source to a write level prior togenerating the instruction for restarting.
 2. The controller of claim 1,wherein the controller generates an instruction for interruption when itis determined that a buffer underrun is likely to occur based on theamount of data stored in the buffer memory.
 3. A controller forcontrolling interruption and restarting data writing to a recordingmedium, wherein writing the data stored in a buffer memory to therecording medium or reading the written data from the recording mediumis performed by selectively providing an optical head performing a laserirradiation with a write laser power source or a read laser powersource, the controller comprising: an address memory for storing atleast one of an address of the recording medium and an address of thebuffer memory when the writing of data to the recording medium isinterrupted, each address indicating a location where the writinginterruption occurred; and a restart circuit for generating aninstruction for restarting the writing of data to the recording mediumby changing the power source provided to the optical head from the readlaser power source to the write laser power source based on the addressstored in the address memory while reading the written data from therecording medium by providing the optical head with the read laser powersource, wherein the restart circuit generates the instruction forrestarting before the location of the data read from the recordingmedium reaches the interruption location.
 4. The controller of claim 3,the timing that the restart circuit generates the instruction forrestarting is set in accordance with the time required for setting thevoltage of the write laser power source to a write level.
 5. Thecontroller of claim 3, wherein the controller generates an instructionfor interruption when it is determined that a buffer underrun is likelyto occur based on the amount of data stored in the buffer memory.
 6. Acontroller for controlling interruption and restarting data writing to arecording medium, wherein writing the data stored in a buffer memory tothe recording medium or reading the written data from the recordingmedium is performed by selectively providing an optical head performinga laser irradiation with a write laser power source or a read laserpower source, the controller comprising: an address memory for storingat least one of an address of the recording medium and an address of thebuffer memory when the writing of data to the recording medium isinterrupted, each address indicating a location where the writinginterruption occurred; a memory for storing data corresponding to awrite level of the voltage of the write laser power source when datawriting to the recording medium is interrupted; and a restart circuitfor generating an instruction for restarting the writing of data to therecording medium by changing the power source provided to the opticalhead from the read laser power source to the write laser power sourcebased on the address stored in the address memory while reading thewritten data from the recording medium by providing the optical headwith the read laser power source.
 7. The controller of claim 6, whereinthe restart circuit generates an instruction for setting the voltage ofthe write laser power source to a write level prior to generating theinstruction for restarting.
 8. The controller of claim 6, wherein thecontroller generates an instruction for interruption when it isdetermined that a buffer underrun is likely to occur based on the amountof data stored in the buffer memory.